Intraluminal medical devices, for example, stents, are employed in a number of medical procedures and their structure and function are well known. Stents are typically cylindrical or tubular radially expandable prostheses introduced via a catheter assembly into a lumen of a body vessel in a configuration having a generally reduced diameter, i.e. in a crimped or unexpanded state, and are then expanded to the diameter of the vessel. In their expanded state, stents support or reinforce sections of vessel walls, for example a blood vessel, which have collapsed, are partially occluded, blocked, weakened, or dilated, and maintain them in an open unobstructed state. They have also been implanted in the urinary tract, in bile ducts, in the alimentary tract, in the tracheobronchial tree, in cerebral aqueducts, in the genitourinary system, in the prostatic urethra, in fallopian tubes, as well as other regions of the body. Stents are advantageous because they can reduce the likelihood of restenosis, and because the patency of the blood vessel is maintained immediately after the intravascular treatment.
Stents are available in self-expanding and in mechanically expandable versions which employ a dilatation balloon for expansion. Both versions are well known and widely available in a variety of designs and configurations, and are made from a variety of materials including plastics and metals with metals being more typically used. Hybrid stents which have self-expanding and mechanically expandable characteristics are also known.
Various methods are employed for delivery and implantation of a stent. For instance, a self-expanding stent may be positioned at the distal end of a catheter around a core lumen. Self-expanding stents are typically held in an unexpanded state during delivery using a variety of methods including sheaths or sleeves which cover all or a portion of the stent. When the stent is in its desired location of the targeted vessel the sheath or sleeve is retracted to expose the stent which then self-expands upon retraction.
Another method includes mounting a mechanically expandable stent on an expandable member, such as a dilatation balloon provided on the distal end of an intravascular catheter, advancing the catheter through a patient's vasculature to the desired location within the patient's body lumen, and inflating the balloon on the catheter to expand the stent into a permanent expanded condition. One method of inflating the balloon includes the use of inflation fluid. The expandable member is then deflated and the catheter removed from the body lumen, leaving the stent in the vessel to hold the vessel open.
The advancement of the stent through a patient's vasculature can involve traversing sharp bends and other obstacles which may require the stent to be highly flexible and trackable.